Phase meter for polyphase currents



March 22, 1932. A. D, ILIOVICI PHASE METER FOR POLYPHASE CURRENTS FileMay 5. 1930 Patented Mar. 22, 1932 F-FI CE AVRAM DAVID ILIOVIGI, OFPARIS, FRANCE, ASSIGNOR TO COMPAGNIE POUR LA l FABRICATION DES COMPTEURSET MATERIEL DUSINES A GAZ, OF MONTROUGE, I

'SEINE, FRANCE, A J OINT-STOGK COMPANY OF FRANCE PHASE METER FORPOLYPHASE GURRENTS Application filed May 5, 1930, Serial No. 449,982,and in France May 6, 1929.

Phase meters with rotating iron armatures are constructed for two-phaseorthree-phase circuits, wherein the iron portion is Z-shaped with theweb practically parallel to the axis of rotation of the movable pointer,while the arms are perpendicular to the axis. The armature is magnetizedby a fixed coil the axis of which coincides with that of the pointer,while through its winding there flows a current generally proportionalto one of the voltages of the circuit the power factor, cos gb, of whichis to be measured. Moreover, a radial rotating magnetic field isproduced by two other coils, in the case of two-phase circuits, or threein the case of three-phase circuits, making between them angles of 1/2or 21/8 respectively and through which flow generally the circuitcurrents or currents proportional thereto.

The action of this field on the magnetized iron armature makes it takeup a position which depends on the cos 1).

This type of phase meter presents the advantage of allowinga scaledeflection of 360 25 and a reduction of the mechanical friction torquewhich may be made absolutely negligible especially as the pointer may bemade much lighter than that of the other types of phase meters.

But the apparatus thus designed, as is the case with the majority ofexisting phase meters, is only suitable when the voltages and currentsare balanced.

It is well known that the voltages are practically balanced-whereas thecurrents generally are not; in this case, the apparatus gives a badlydefined cos 5. r

If the coil magnetizing the iron be fed with one of the currents of thecircuit and the other coils with currents proportional to and in phasewith the voltages, the phase meter measures the phase displacement ofthe current utilized relatively to the corresponding M, voltage orrelative to another suitable volt- But it is possible to construct aphase meter measuring the mean cos S of a two-phase or three-phasecircuit with two or three rotating armaturessecured together and asuitable number of fixed coils. A solution of this problem has beenindicated in French Patent No. 597,582 dated May 4th, 1925 (Fig. 4)

The present invention is directed to a simpler solution using a rotatingpointer with two or three armatures each magnetized by a suitable coil,the unit formed by the armatures moving through a single magnetic fielldproduced by two or three suitably fixed CO1 s.

Vv hen the phase meter is to be used to measure the mean cos of atwo-phase circuit, theapparatus may include two armatures magnetized bytwo coils traversed by currents proportional to the voltages and movingin the magnetic field produced by two practically identical coils fromthe electric point of view, said coils through which flow the currents,having their axes mutually perpendicular and perpendicular to the axisof rotation of the armatures.

In a three-phase circuit, there maybe used three movable armaturessecured together, and magnetized by three practically identicalcoilsthrough which flow currents proportional to three voltages of thethree-phase system, said armatures moving in the magnetic field producedby three practically identical coils whose axes which are perpendicularto the axis of rotation of the movable pointer form between them anglesof 120. The three currents of the circuits or currents prqportionalthereto may flow through said 001 s.

The number of armatures may be reduced to two as also the number ofcoils magnetizing them, by converting the three-phase voltage systeminto a two-phase system by means of transformers, or Scottauto-transformers or other equivalent devices.

Likewise, the number of field producing coils may be reduced to two, byconverting the system of three-phase currents intoan equivalenttwo-phase system.

On the contrary, in order to secure a uniform scale for the apparatus,it may be ad.- visable to multiply the number of coils by producing awinding similar to thestator of an induction motor. I

Instead ofcausing currents proportional tothe voltages to flow throughthe coils for magnetizing the armatures, currents equal or proportionalto those of thecircuit whose cos is being measured, may be passedthrough said coils, and, on the other hand, currents proportionalto thevoltages maybe passed in the coils which produce the field which reactson the armatures.

The invention has been illustrated by way i exam' lein the followingdrawings wheres 1n: I

Fig. 1 illustrates the phase meter accord ing to the invention insectional elevation.

Fig. 2 is a plan view of the phase meter illustrated in Fig. 1. v I Fig.3 shows a circuit arrangement for the wiringoi the phase meter. Figs:ite 7 are vector diagrams explanator iyhof the operation of the-phasemeter.

7 ephase meterof Figs. 1 and 2 has two annatures at right-angles whichare magnetized by twoycoils through which flow currents proportional .totwo two-phase voltages obtained, as shown in Fig. 3, by means of a Scottdevice; the magnetic field through which the armatures movebeing-obtained by means oft-hree coils traversed by the'currents. j Inthese Figures, F F and F F 2 are the vanes of the two armatures, theWebs of which are formed by iron tubes C and C2.

surrounding the axisof the movable pointer; theyarmatures F C F andfF CF are=magnetized by the coils 1),.1) through which two suitablealternating currents are causedtoflow. It willbe assumedthat the virtualvalues of thesecurrents are proportional. to the common virtual valuecofthe voltagesof the circuit, the phase displacement of which it isdesired to measure.

. in%magnetizat1on.

Underthe action ofthese currents, the armatures F G F F C F receivealternat- 1 B B are three coils of a three-phase systemthrough whichflow the three currents 'of the-three-phasecircuit, the cos of which itis desired to measure (or by three proportiona-l currentsobtainedbymeans of current transformers). Said coils produce: in the space inwhich the armatures move a radial rotating magnetic field which actingon the armatures causes them to takeupa resultant position which, aswillbe seen presently, de-

pends on the. phase displacements between the currents in theaforementioned coils b,

b, and thecurrents in the coils B B B Dis a metallic disc (generallycopper or Y aluminium) moving in the air gap of one orame-themovablesystem; S :is the base of the apparatus, p posts servingto support the dial and :thejlidf; and F are soft iron memberssurrounding thephase. meter in order to re duce the effect of the outermagnetic fields and, in particular,those of the magnets A on theoperating parts of the apparatus and in particular the movablearmatures. The member E may, for example, have .theform of a basin wh leF has the form of acylindrical tube.

Fig. 3 shows the phase meter forming the object 'of the invention wiredto a. thresphase circuit. In this figure the phase outlined by thecircle in double lines, comprises the coils I), Z)" which magnetize themovable (line voltages of r armatures and the coils 13 ,13 B which pro-1 phase system forfeedingtthe coils -b, b T

T T are three current transformerswhichcause currents proportional toand practically in phase with'the currents in theawires, 1, 2.

and3 to flow through the coils B B 8,.

The operation of. the phase meter will be readily understood. Thealternatinggcurrents whichflow through the coils bgbf (Fi s 1 and. 3).magnetize the movable giron" vanes giving-k them. alternating;magnetizations;

.The mean direction of thelihesof' force-in the yan'es (for example F F'coincides with the axes of said vanes; each movable armature isequivalent to a magnet, themag-i netic moment of which- (M for thearmature,

F f zfor the armature FL .05

F is perpendicularto the axis'joffrotation and is parallel 'to the'axisofthe twovane's.

which form the armature under considera tion. Thus, for example, for thearmature, F C F the magnetic moment is"represented in Fig.- 4rby Msaidmomentis proportionahtmoreover, to the current i in the coil b,hence to the voltage c' at theterminalscofsaid coils Ifthe reactance ofthe coils?) is negligible in comparisoniw'ith itsresistance, a,and=henceM ,is in phase with v, and therefore: 1 p

or M Mm, sin t (1) I of thevoltage c I I 1 Similarly in the case ofthemoment M ofithe armature 1 ,0 F'

r by COS (o said moment being in the direction? of" the axis oflthearmature (Fig-f4) in phabewithi the voltage 0 atthe terminals of thecoil'b': and: the maximum value- Mm of; which is 'Mm being proportionalto the virtual value proportional to the virtual value of the volta e o'If the system of voltages at the terminals of the three-phase circuit isbalanced, the two voltages 0' and 'v formed by the Scott device S havethe same virtual value which is proportional to the virtual value V ofthe voltages of the three-phase system. Moreover, the voltage 12 is inphase with the phase voltage of the third phase. The coils b, b and thearmatures being identical, the values Mm and Mm are equal and theirknown value M is proportional to V; hence M =7aV sin (n t (1) M =kV cosc) t (2) and M being moreover in phase, and hence M in quadrature, withthe voltage of the third phase of the three-phase circuit in question.

But the diagram of Fig. 5 shows that the alternating magnetic moment Mmay be considered as resulting from two magnetic moments M and M ofconstant numerical value:

rotating in contrary directions at angular velocity w, M being thecomponent of the moment rotating in the direction of the arrow f, and M"the one which rotates in the direction f.

Similarly, the diagram of Fig. 6 shows that the moment M may be resolvedinto two moments h and M similar to the preceding ones.

The two magnetized armatures being con nected together may be replacedby a single magnetized armature, the magnetic moment of which is theresultant of the two moments M M or of the four moments M, M", M and l\into which the first are resolved. It will be seen immediately from Fig.7 that the value of the resultant moment is:

and that it rotates at angular velocity (u in the direction of the arrowf.

The preceding remarks may be interpreted as follows The group ofarmatures F C F and F C F magnetized by the alternating currents of thecoils b, b is equivalent to a magnet of constant magnetic moment butwhich rotates relatively to the armatures at constant angular velocityin the direction of the arrow 7 (Fig. 7). The axis of said magnetequivalent to the magnetized armatures has moreover at the instant t=0the direction of the axis 0A of the vanes F F (Figs. 4 and 7).

This being so, it will be assumed for the moment that the currents inthe three phases '1, 2, 3 of the circuit form a balanced system.

given by:

. H Zcl,

I being the virtual Value of one of the currents of the three-phasecircuit. It is known moreover, that the direction of the field H is thatof the axis of one of the coils, for example of the coil B when thecurrent in said coil is a maximum.

If the current in the coil B lags by an angle (,0 on the voltage of thesame phase, it can be expressed by the relation:

and will therefore pass through its maximum at the instant It thereforefollows that at the instant I the rotating field H will be in thedirection of the axis of the coil B and, at the instant i=0 it isdisplaced relatively to this position by the angle to. There is finallyobtained a field H and a magnet M rotating in the. same direction at thesame speed w; the magnet having no resisting torque to overcome(neglecting the friction of'the armatures) sets in the direction of thefield. Now the position of the first at the instant t=0 being that ofthe axis of the vane F, and the. field being displaced by (p relativelyto the axis of the coil B the result is that the axis of the vane Fmakes an angle (p with the axis of the coil B Hence the apparatusmeasures the phase displacement of the circuit. 7

Assuming now that the currents 2' 2' 71 in the circuit are unbalancedWhile the voltages remain balanced, then in this case the positive phasesequence components of the currents give a field rotating in the samedirection as in the preceding case andsaid field acts on the armaturesas in the preceding case. Moreover, the system of negative phasesequence components of the currents gives a field rotating in theopposite direction to the magnet equivalent to the armatures. Now when afield rotates at uniform speed relatively to a magnet, it producesthereon a zero mean torque.

:7 To sum up, in the case of unbalancedv cur;

rents, the system of the positive phase. se

"quence componentsaloneracts on the magnetized armaturesand thereforeforces the latter to take up a: position which. depends on the phasedisplacement (p between said sys'- temand the system of the three-phasevoltages a I claim: v

1. In a phase meter for measuring! the power factorof a polyphasecircuit Whether balanced or unbalanced, the combination of at least twoZ-shaped movable magnetizable elements secured together, a set of coilsfor magnetizing said elements, a single set of coils for producing arotating magnetic field in which all said elements move, said two setsof coils being ied respectively with the currents an'dcvoltages of thepolyphase circuit.

f2. In a" phase meter for measuring the power factor of a poly hase',circuit whether alanced or unbalance the combination of at least twoZ-shaped movable magnetizable elements secured together and displacedthrough ninety degrees, a set offlcoils, for

magnetizing said elements, a single setof' coils for producing arotating magnetic field in which all said elements move, said two setsOfi'COllS being fed respectively'with the currents and voltages of thepolyphase circuit. r I

3, In a phase meter for measuring the power, factor of. a three-phasecircuit whether balanced or unbalanced, the combination of 'atleast two:Z-shaped movable magnetizable elements secured together, a set ofcoilsfor ma netizi-ng said elements, a single set of coils or producingarotating mag;

netic field in which all .saidelements move,

and meansffor converting one of. the two three-phase systems, voltagesand currents,

of' said three-phase circuit into two-phase and feeding-the same to oneof said sets ofi CQilS,1tl1 Otl1B1 set "o f;coilsbeing'fedffromtheotherunconvertedfthree-phase system. J

4, In a'phasemeter for measuring, the

power factor of a three-phase circuit whether balanced or unbalanced,the combination of at least two Z-shaped movable magnetizable elementssecured together and dislac'ed thrOugh'ninety degrees, a set ,OfrCOllSor magnetizing said elements, asingle set of' 'coils for producing'arotating magnetic field in which all said elements move, and means forconverting one of the two threephasesystems, voltages and currents, ofsaid three-phase circuit into two-phase and feedin the sameto one ofsaidsets of coils, the other set of coils being fed fromthe otherunconverted three-phase system. I

AVRANL'DAVID' ILIOVICL

